Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$147.52	13.668%	$167.683	$167.68	$167.70	$167.70
Purchase #2	$84.78	6.853%	$90.59	$90.59	$90.60	$90.60
Purchase #3	$103.99	8.606%	$112.9394	$112.94	$112.95	$112.90
Purchase #4	$218.72	4.397%	$228.3371	$228.34	$228.35	$228.30
Purchase #5	$37.79	4.448%	$39.4709	$39.47	$39.45	$39.50
Purchase #6	$135.39	12.790%	$152.7064	$152.71	$152.70	$152.70
Purchase #7	$221.32	3.637%	$229.3694	$229.37	$229.35	$229.40
7 purchase totals =	$949.51		$1,021.0962	$1,021.10	$1,021.10	$1,021.10